The average temperature was 52.9 degrees Fahrenheit, or 4.5 degrees above average, the NOAA said on Monday. Twenty-eight states east of the Rockies set temperature records for the six-month period. The 12 months ending June 30 was the warmest 12-month period of any on record, according to the NOAA.

Record-breaking temperatures blistered most of the United States in June, with more than 170 all-time temperature records broken or tied during the month. On June 28 in Norton, Kansas, for instance, the temperature reached 118 degrees, an all-time high. On June 26, Red Willow, Nebraska, set a temperature record of 115 degrees, eclipsing the 114-degree mark set in 1932.

The first six months of the year were also drier than most, with precipitation totals 1.62 inches below average. According to the U.S. Drought Monitor, more than half of the country (56 percent) experienced drought conditions--the largest percentage in the 12-year history of the service.